Modern day semiconductor devices are typically formed by changing the electrical characteristics of a semiconductor material (e.g., a silicon substrate) through implanting dopants into the bulk of the material. By changing the type and/or concentration of implanted dopants (e.g., n-type dopants, p-type dopants) the current conduction characteristics of a device can be changed. Current conduction occurs by forming free charge carriers (e.g., electrons, holes) in the bulk of the semiconductor material. Through doping the material with impurity dopant atoms (e.g., phosphorus or boron) the number of free charge carriers can be greatly increased resulting in different current conduction characteristics. Semiconductors containing an excess of holes are called p-type devices and semiconductors containing an excess of electrons are called n-type devices.
For example, the simplest semiconductor device is a p-n junction diode comprising a semiconductor surface having two regions, with different dopant types, abutted together (e.g., a p-type material in contact with an n-type material) at a junction. When an electric potential is applied across the junction of the device (i.e., an electric field is present in the bulk of the device) charge carriers (e.g., electrons) freely flow from one region (e.g., the n-type region) to the other region (e.g., the p-type region), where they recombine with opposite charge carriers (e.g., holes) and form a depletion region in the vicinity of the junction.
More complex device topologies, having more sophisticated geometries, may also be formed based upon the basic idea of semiconductor doping. These more complex devices may be formed to provide devices that meet the needs of the modern computing industry.